RESPONSES OF ROD BIPOLAR CELLS IN THE DARK-ADAPTED RETINA OF THE DOGFISH, SCYLIORHINUS-CANICULA
RESPONSES OF ROD BIPOLAR CELLS IN THE DARK-ADAPTED RETINA OF THE DOGFISH, SCYLIORHINUS-CANICULA
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DOI：
10.1113/jphysiol.1980.sp013155
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发表时间：
1980-01-01
影响因子：
5.5
通讯作者：
FALK, G
中科院分区：
文献类型：
--
作者：
ASHMORE, JF;FALK, G
Responses to light were recorded from bipolar cells in the retina of the dogfish, S. canicula, under dark-adapted conditions. The identity of the cells was confirmed by Procion Yellow staining. More than 95% of the bipolar cells were of the type which depolarized to a spot of light. These are termed depolarizing bipolar cells. In most cells illumination of the surround had little effect on the responses elicited from the central receptive field. The mean flash sensitivity of the depolarizing bipolar cells was 270 mV/Rh (Rh signifies rhodopsin photoisomerization per rod for full field illumination). The mean flash sensitivity of horizontal cells under the same conditions was 8 mV/Rh. In a limited sample of hyperpolarizing bipolar cells the highest flash sensitivity was 42 mV/Rh. The high flash sensitivity of the depolarizing bipolar cells indicates a large voltage gain at its synapse with rods. If rod flash sensitivity was 2 mV/Rh, the mean gain at the synapse would be 135, but for some cells the gain was in excess of 500. Responses of depolarizing bipolar cells to dim flashes could be approximated by the impulse response of a 12-16 stage low-pass filter. Horizontal cell responses could be fitted by a low-pass filter of 6 sections. The implied filter at the rod-bipolar cell synapse is tuned to the higher frequency components of rod signals, improving temporal resolution in the rod pathway. Depolarizing bipolar cell responses to test flashes are reduced by weak background illumination (less than 0.1 Rh/s). This desensitization, which would not be expected to affect rod responses, could be explained by a shift in the operating point to a less sensitive region of the intensity-response curve as a result of the large depolarization elicited by the background. Current injection into the cell in darkness and during light response is consistent with the release of a transmitter by rod terminals which closes ionic channels in a conductance path having a reversal potential of -8 mV, transmitter release suppressed by light.
